1. Field of the Invention
The present invention relates to a perpendicular magnetic recording head for recording on a medium surface of a recording medium such as a disk by providing a magnetic field in the perpendicular direction, and more specifically, a perpendicular magnetic recording head capable of reducing the width of magnetization reversal (width of magnetization transition) between recording patterns recorded on the recording medium, which are magnetized reversely from each other, and approximating the magnetic field line on the trailing side of the recording patterns to the direction parallel with the direction of the width of the track, and a method of manufacturing the same.
2. Description of the Related Art
A magnetic head shown in FIG. 26 is a structure (partial cross-sectional view) of a perpendicular magnetic recording head in the related art. The perpendicular magnetic recording system of magnetizing the medium in the perpendicular direction with respect to the medium surface of the recording medium can record magnetic data with high degree of density in comparison with a system of magnetizing the medium in the horizontal direction with respect to the medium surface.
Reference numeral 1 designates a main magnet pole layer and reference numeral 2 designates a return yoke layer. In the vertical magnetic recording head shown in FIG. 26, the return yoke layer 2 is provided on the leading side when viewed from the main magnet pole layer 1 (lower side in the drawing). The perpendicular magnetic recording head of this type is referred to as a single magnet pole head.
A recording medium 3 has, for example, a disk shape, and includes a soft layer having a high magnetic transmission coefficient (lining layer) 3a, a non-magnetic intermediate layer 3b for aligning the crystalline orientation of a recording layer 3c, and the recording layer 3c having a high coercive force and formed mainly of Co laminated in sequence from the bottom.
The vertical recording head shown in FIG. 26 provides the perpendicular magnetic field to the recording medium 3, and magnetizes the recording layer 3c of the recording medium 3 in the perpendicular direction.
The recording medium 3 is rotated about the center of the disk as the center of axis of rotation, and the recording medium 3 moves from the leading side to the trailing side of the perpendicular magnetic recording head which rises from the recording medium 3 as shown in FIG. 26.
As shown in FIG. 26, a recording magnetic field 4 is generated from the main magnet pole layer 1 toward the recording medium 3, and the recording magnetic field 4 passes through the recording layer 3c--> the intermediate layer 3b--> the soft layer 3a of the recording medium 3, and then comes back to the return yoke layer 2. The recording layer 3c is magnetized in the perpendicular direction by being provided with the perpendicular magnetic field from the main magnet pole layer 1. As shown in FIG. 26, however, since the distance from the front end surface of the main magnet pole layer 1 to the soft layer 3a is long, the recording magnetic field 4 spreads isotropically from the main magnet pole layer 1 to the recording medium 3 in the single magnet pole head, and as shown in FIG. 27, when the recording pattern recorded on the recording medium 3 was observed by the magnetic force microscope (MFM), it was found that the magnetic field line on the trailing side of the recording pattern is curved into the trailing direction from the edge to the center.
When the magnetic field line on the trailing side of the recording pattern recorded on the recording medium 3 is curved, there arose a problem that the reproducing output which is obtained when the reproduction device such as a MR head or the like is traveled on the recording pattern was deteriorated.
On the magnetic field line on the trailing side, since the magnetic field line on the trailing side is curved, the reproduction device reads the adjacent recording pattern of reversed magnetization as well, thereby generating noise.
In the case of the single magnet pole head provided with the return yoke layer 2 on the leading side when viewed from the main magnet pole layer 1 as shown in FIG. 26, the recording magnetic field 4 spreads isotropically from the main magnet pole layer 1 as described above, and the strength of the recording magnetic field 4 is decreased as it spreads toward the trailing side or the leading side. Since the recording medium 3 moves from the leading side to the trailing side of the perpendicular magnetic recording head, the isomagnetic line spread toward the trailing side is overwritten on the magnetic field line on the leading side of the recording pattern recorded previously on the magnetic medium 3. Therefore, the recording magnetic field which has low strength spreading toward the trailing side causes a phenomenon to increase the width of magnetization reversal (width of magnetization transition) between the recording patterns which are magnetized reversely from each other. Therefore, there is a problem such that when the reproduction device is traveled on the recording pattern, increased noise of magnetization reversal is generated in the obtained reproduction output due to the wide width of the magnetization reversal. Consequently, the single magnet pole head shown in FIG. 26 is a structure in which the S/N ratio is significantly undesirable.
Patent Documents shown below disclose an improved structure of the main magnet pole layer of the single magnet pole head shown in FIG. 26 (Japanese unexamined patent application publication No.2002-279606), or a shield pole structure provided with the return yoke layer on the trailing side when viewed from the main magnet pole layer (US2003/0117749 A1, JP-A-2002-92820).
In Japanese Unexamined Patent Application Publication No.2002-279606, as shown in FIG. 1, for example, the upper surface side (trailing side) of the main magnet pole layer 1 has a concave shape. The effects of such a shape is described in the patent publication such that “Accordingly, there is provided the perpendicular recording magnetic head which enables recording of the bits without bending the shape of the magnetization reversal and is free from such problems that the width of magnetization reversal looks larger when reproducing the magnetic resistant effect type head thereby increasing the half width of the solitary wave and the width of recording track is reduced with increase in track recording density . . . ([0012]in Specification of Japanese Unexamined Patent Application Publication No.2002-279606).
However, since the device disclosed in Japanese Unexamined Patent Application Publication No.2002-279606 is the single magnet pole head, the broadening of the width of magnetization reversal cannot be reduced. As shown in FIG. 28, according to the perpendicular magnetic recording head in Japanese Unexamined Patent Application Publication No.2002-279606, it is considered that particularly the portion near the center of the magnetic field line on the trailing side of the recording pattern can be approximated to the direction parallel with the direction of the width of the track. The shape of the magnetic field line on the trailing side is significantly influenced by the shape of the end surface of the main magnet pole layer on the trailing side. In other words, in the perpendicular magnetic recording head shown in FIG. 26, the end surface of the main magnet pole layer 1 on the trailing side is flat surface. In this case, as shown in FIG. 27, since the portion of the magnetic field line on the trailing side of the main magnet pole layer near the center is bent toward the trailing direction, it is considered that the portion of the magnetic field line on the trailing side of the recording pattern near the center can be controlled to a substantially flat shape as shown in FIG. 28 by forming the end surface of the main magnet pole layer on the trailing side into a concave shape as shown in Japanese Unexamined Patent Application Publication No.2002-279606.
However, as shown above, since the device in Japanese Unexamined Patent Application Publication No.2002-279606 is the single magnet pole head, the recording magnetic field generated from the main magnet pole layer is spread isotropically as described in conjunction with FIG. 26, and consequently, as shown in FIG. 28, the width of the magnetization reverse (width of magnetization transition) between the recording patterns which are magnetized reversely from each other increases, and the noise of magnetization reversal due to the broadening of the width of the magnetization reversal cannot be reduced suitably. Therefore, the S/N ratio cannot be improved even with the perpendicular magnetic recording head in Japanese Unexamined Patent Application Publication No.2002-279606.
US2003/0117749 A1 discloses a shield pole structure in which the return yoke layer (return pole) 206 is formed on the trailing side when viewed from the main magnet pole layer (main pole) 204 in the perpendicular magnetic recording head as shown in FIG. 5 and FIG. 6. Reference numeral 201 represents a traveling direction of the reproduction/recording head 200.
In the perpendicular magnetic recording head having such a shield pole structure, since the return yoke layer 206 exists on the trailing side, it is considered that the recording magnetic field generating from the main magnet pole layer 204 can hardly spread isotropically toward the trailing side, and consequently, the width of magnetization reversal (width of magnetization transition) between the recording patterns, which are magnetized reversely from each other can be reduced.
However, as shown in FIG. 29, since the end surface of the main magnet pole layer 204 on the trailing side is a flat surface, the same problem as in the single magnet pole head described in conjunction with FIG. 26 and FIG. 27, that is, the problem that the magnetic field line on the trailing side of the recording pattern protrudes toward the trailing side from the edges to the center cannot be solved yet, and consequently, lowering of the output or deterioration of the S/N ratio is resulted.
In Japanese Unexamined Patent Application Publication No.2002-92820, a perpendicular magnetic recording head of the shield pole type is disclosed as in US2003/0117749 A1. In Japanese Unexamined Patent Application Publication No.2002-92820, as shown in FIG. 4, a projecting portion 36 projecting toward the main magnet pole 31 is provided on the end surface of the return path magnet pole layer 32 on the leading side. With the provision of such a projecting portion 36, this patent publication describes “Broadening of the magnetic field distribution at the track edge, which is caused by broadening of the magnetic flux in the direction of the width of the track when the magnetic field passes through the soft magnetic layer of the recording medium from the main magnet pole, can be restrained. Therefore, formation of the sharp track edge is enabled, whereby improvement of the track density by narrowing the track width is achieved.” (See [0028] in Specification of Japanese Unexamined Patent Application Publication No.2002-92820).
However, since the end surface of the main magnetic pole 31 on the trailing side is flat surface also in the perpendicular magnetic recording head of the shield pole type disclosed in Japanese Unexamined Patent Application Publication No.2002-92820 as in the case of US2003/0117749 A1, the problem that the magnetic field line on the trailing side of the recording pattern protrudes toward the trailing side from the edges to the center cannot be solved yet, and consequently, lowering of the output or deterioration of the S/N ratio is resulted. In addition, in the Japanese Unexamined Patent Application Publication No.2002-92820, the width of magnetization reversal is wider at the position near the edge of the magnetic field line on the trailing side as will be described referring to FIG. 5, and hence there arises a problem such that when the reproduction device travels on that position, the noise of magnetization reversal increases and hence deterioration of the S/N ratio is resulted.